There is the possibility MM could knock Bob out. Blue Marvel did it, actually knocking Robert into orbit. However, Robert was able to shake it off, dive bombed Adam and knocked him out. They were very closely matched.

I do however, tend to think that fight was a little dumbed down for Robert, and I have had to rethink a number of potential match-ups with the Sentry, particularly after re-reading is '05 mini a few months ago and a few of his other appearances in other magazines (Mighty Avengers, Dark Avengers). I was astounded.

- has literally, one handed, defeated Terrax and broke his axe in half.

- a number of the world's hereos assisted in "helping" Robert. He had erased the memories of every one on the planet of his existence, including the world's most powerful telepaths, Xavier included.

- had to "allow" Emma Frost into his mind so she could help him.

- tore through Dr Strange's auto shields

- re-integrated himself after being disintegrated by the Molecule Man

- came back to out time line from a time BFR by Morgan LeFay

- as the Void (his true identity), he broke every bone in the Hulk's body.

- we know what he did to Loki and Ares

- burst through eight floors of steel lined adamantium walls on his way out of the "Raft" prison

Therefore, one of J'on's greatest assets, his telepathy is questionable in it's effectiveness against the Sentry. I've also seen J'on struggle against the insane (which Robert decidedly is...he's a schizophrenic agorophobic):

It would seem no matter what J'on could possibly do to Robert in a physical way could be undone because of his complete control over his body on the molecular level. I gotta go with the Sentry.

could go either way sentry is stronger faster and has better energey manipulation but mm has better telepathy and has a bunch more powers. if mm phazed sentry could un phaze him with matter manipulation it depends on if mm control over his own mollecular structer is stronger then sentry's matter manipulation.